We report on the possibility of describing the absorption and emission characteristics of an ensemble of silicon nanocrystals (NCs) with realistic distributions in the NC size, by the sum of the reponses of the single NCs. The individual NC responses are evaluated by means of ab initio theoretical calculations and the summation is performed by taking into account the trend of the optical properties as a function of NC size and oxidation degree. The comparison with experimental results shows a nice matching of the spectra, also without any tuning of the parameters. Finally, the possibility of adapting the model in order to reproduce the experimental data is explored and discussed.
In battery electric buses (e-buses), the substantial energy consumption of the heating, ventilation, and air conditioning (HVAC) system can cause significant reductions of the available travel range. Additionally, HVAC systems are often operated at higher levels than what required for the thermal comfort of the passengers. Therefore, this paper proposes a method to experimentally investigate the influence of the HVAC system on the energy consumption and thermal comfort in a 12m e-bus. An appropriate thermal comfort model is identified and the required climatic input parameters are selected and measured with self-developed sensor stations. The energy consumption of the e-bus, the state of charge (SoC) of the battery and the available travel range are measured by an embedded data logger. Climatic measurements are then performed with heating on and off on a Berlin bus line in winter conditions. The results show that the energy consumption of the e-bus is increased by a factor of 1.9 with heating on, while both the SoC and travel range are reduced accordingly. Comparing the thermal comfort with heating on and off, a decrease from “comfortable” to “slightly uncomfortable but acceptable” is observed.
This paper evaluates the performance of a hybrid reluctance actuator for application in high-precision motion systems. For this purpose, its properties are compared with those of a voice coil actuator, which is the choice actuator for many high-precision applications. To properly investigate the non-linearities of these systems, finite element analysis (FEA) is employed. Spacial-domain analysis shows that the hybrid reluctance actuator can deliver both higher forces per volume (by a factor up to app. 10.5) and thrust constant (by a factor up to app. 9.6) than the voice coil actuator. However, these values depend strongly on the position of the mover, causing a high non-linear stiffness. Frequencydomain analysis yields the power losses of the actuators, as well as the dynamic thrust constant. It is shown that at all frequencies the hybrid reluctance actuator suffers from higher iron loss (by a factor up to app. 5.1) than the voice coil actuator. Additionally, its thrust constant shows a large magnitude slope (app. −14.4 dB/dec) and phase lag (app. −71 • at f =10 kHz) in the frequency domain, resulting in a narrowed control bandwidth. These results clearly indicate a trade-off between thrust constant, linearity and dynamic behavior, which should be considered for employment in high-precision applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.